Reproducibility of haptic waveform

ABSTRACT

A system may include an electromagnetic load capable of generating a haptic event and a haptic processor configured to receive at least one first parameter indicative of a desired perception of the haptic event to a user of a device comprising the electromagnetic load, receive at least one second parameter indicative of one or more characteristics of the device, and process the at least one first parameter and the at least one second parameter to generate a driving signal to the electromagnetic load in order to produce the desired perception to the user despite variances in the device that cause an actual perception of the haptic event to vary from the desired perception.

CROSS-REFERENCES AND RELATED APPLICATION

This present disclosure is a continuation of U.S. patent applicationSer. No. 17/038,068, filed Sep. 30, 2020, issued Jul. 5, 2022 as U.S.Pat. No. 11,380,175, which claims benefit of U.S. Provisional PatentApplication Ser. No. 62/925,307, filed Oct. 24, 2019, each of which isincorporated by reference herein in its entirety.

FIELD OF DISCLOSURE

The present disclosure relates in general to methods, apparatuses, orimplementations for haptic devices. Embodiments set forth herein maydisclose improvements to how haptic events are created, specified, andstored.

BACKGROUND

Vibro-haptic transducers, for example linear resonant actuators (LRAs),are widely used in portable devices such as mobile phones to generatevibrational feedback to a user. Vibro-haptic feedback in various formscreates different feelings of touch to a user's skin and may playincreasing roles in human-machine interactions for modern devices.

An LRA may be modelled as a mass-spring electro-mechanical vibrationsystem. When driven with appropriately designed or controlled drivingsignals, an LRA may generate certain desired forms of vibrations. Forexample, a sharp and clear-cut vibration pattern on a user's finger maybe used to create a sensation that mimics a mechanical button click.This clear-cut vibration may then be used as a virtual switch to replacemechanical buttons.

FIG. 1 illustrates an example of a vibro-haptic system in a device 100.Device 100 may comprise a controller 101 configured to control a signalapplied to an amplifier 102. Amplifier 102 may then drive a vibrationalactuator (e.g., haptic transducer) 103 based on the signal. Controller101 may be triggered by a trigger to output to the signal. The triggermay, for example, comprise a pressure or force sensor on a screen orvirtual button of device 100.

Among the various forms of vibro-haptic feedback, tonal vibrations ofsustained duration may play an important role to notify the user of thedevice of certain predefined events, such as incoming calls or messages,emergency alerts, and timer warnings, etc. In order to generate tonalvibration notifications efficiently, it may be desirable to operate thehaptic actuator at its resonance frequency.

The resonance frequency f₀ of a haptic transducer may be approximatelyestimated as:

$\begin{matrix}{f_{0} = \frac{1}{2\pi\sqrt{CM}}} & (1)\end{matrix}$

-   -   where C is the compliance of the spring system, and M is the        equivalent moving mass, which may be determined based on both        the actual moving part in the haptic transducer and the mass of        the portable device holding the haptic transducer.

Due to sample-to-sample variations in individual haptic transducers,mobile device assembly variations, temporal component changes caused byaging, and use conditions such as various different strengths of a usergripping of the device, the vibration resonance of the haptic transducermay vary from time to time.

FIG. 2 illustrates an example of a linear resonant actuator (LRA)modelled as a linear system. LRAs are non-linear components that maybehave differently depending on, for example, the voltage levelsapplied, the operating temperature, and the frequency of operation.However, these components may be modelled as linear components withincertain conditions. In this example, the LRA is modelled as a thirdorder system having electrical and mechanical elements. In particular,Re and Le are the DC resistance and coil inductance of the coil-magnetsystem, respectively; and Bl is the magnetic force factor of the coil.The driving amplifier outputs the voltage waveform V (t) with the outputimpedance Ro. The terminal voltage V_(T)(t) may be sensed across theterminals of the haptic transducer. The mass-spring system 201 moveswith velocity u (t).

A haptic system may require precise control of movements of the haptictransducer. Such control may rely on the magnetic force factor Bl, whichmay also be known as the electromagnetic transfer function of the haptictransducer. In an ideal case, magnetic force factor Bl can be given bythe product B·l, where B is magnetic flux density and l is a totallength of electrical conductor within a magnetic field. Both magneticflux density B and length l should remain constant in an ideal case withmotion occurring along a single axis.

As described above, when a current is passed through the coil of theelectromagnet, the electromagnet may experience a force due to theinteraction of the electromagnet and a permanent magnet. A vibrationalactuator 103 may be mechanically mounted to the structure of device 100in such a way that the vibrations due to the moving mass are transferredto the device so it can be felt by a user. In most portable electronicdevices, vibrational actuator 103 is driven from a low output impedanceamplifier 102 with a voltage waveform. However, a user may experience ahaptic event due to the acceleration of a mass in vibrational actuator103, working against the mass of the rest of device 100, as well as theuser's hand. For a given voltage waveform applied, different vibrationalactuators 103 in different devices 100 may experience differentacceleration waveforms. This acceleration may depend on many variables:the resonant frequency of vibrational actuator 103; the mass value andspring designs of vibrational actuator 103; the direction of travel ofthe mass within vibrational actuator 103 relative to device 100 (X, Y orZ-axis); as well as how vibrational actuator 103 is mounted to device100. The acceleration may also vary based on the total mass of device100 and a location of vibrational actuator 103 relative to other itemswith significant mass within device 100.

A further problem is that vibrational actuators may have manufacturingtolerances that cause their haptic response to vary from unit to unitand also vary with temperature and other environmental conditions.

A desired haptic event may be designed by various methods. Such hapticevent may then be processed offline to compute a voltage waveform thatgenerates the desired haptic event when that voltage waveform is appliedto vibrational actuator 103 in device 100. Such processed waveform maybe stored in device 100.

However, such offline (or open loop) pre-processing of the intendedwaveform may have limitations. The waveform may be designed for atypical version of the device 100, and variations of device 100 (e.g.,manufacturing variations of the same model of device 100, variationsbetween models and/or manufacturers of model 100, etc.) and thevibrational actuator 103 may cause the haptic event to be feltdifferently across multiple units of device 100. Additionally, a singledevice 100 may not reproduce the desired haptic event if the temperature(or other parameter) of the device changes from the temperature (or suchother parameter) when the waveform was designed.

SUMMARY

In accordance with the teachings of the present disclosure, thedisadvantages and problems associated with existing approaches forgenerating a haptic waveform for an electromagnetic transducer may bereduced or eliminated.

In accordance with embodiments of the present disclosure, a system mayinclude an electromagnetic load capable of generating a haptic event anda haptic processor configured to receive at least one first parameterindicative of a desired perception of the haptic event to a user of adevice comprising the electromagnetic load, receive at least one secondparameter indicative of one or more characteristics of the device, andprocess the at least one first parameter and the at least one secondparameter to generate a driving signal to the electromagnetic load inorder to produce the desired perception to the user despite variances inthe device that cause an actual perception of the haptic event to varyfrom the desired perception.

In accordance with embodiments of the present disclosure, a method mayinclude receiving at least one first parameter indicative of a desiredperception of a haptic event to a user of a device comprising anelectromagnetic load capable of generating the haptic event, receivingat least one second parameter indicative of one or more characteristicsof the device, and processing the at least one first parameter and theat least one second parameter to generate a driving signal to theelectromagnetic load in order to produce the desired perception to theuser despite variances in the device that cause an actual perception ofthe haptic event to vary from the desired perception.

Technical advantages of the present disclosure may be readily apparentto one having ordinary skill in the art from the figures, descriptionand claims included herein. The objects and advantages of theembodiments will be realized and achieved at least by the elements,features, and combinations particularly pointed out in the claims.

It is to be understood that both the foregoing general description andthe following detailed description are examples and explanatory and arenot restrictive of the claims set forth in this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present embodiments and advantagesthereof may be acquired by referring to the following description takenin conjunction with the accompanying drawings, in which like referencenumbers indicate like features, and wherein:

FIG. 1 illustrates an example of a vibro-haptic system in a device, asis known in the art;

FIG. 2 illustrates an example of a Linear Resonant Actuator (LRA)modelled as a linear system, as is known in the art;

FIG. 3 illustrates selected components of an example host device, inaccordance with embodiments of the present disclosure; and

FIG. 4 illustrates a flow chart of an example method for reproducing ahaptic waveform at an electromagnetic transducer, in accordance withembodiments of the present disclosure.

DETAILED DESCRIPTION

The description below sets forth example embodiments according to thisdisclosure. Further example embodiments and implementations will beapparent to those having ordinary skill in the art. Further, thosehaving ordinary skill in the art will recognize that various equivalenttechniques may be applied in lieu of, or in conjunction with, theembodiment discussed below, and all such equivalents should be deemed asbeing encompassed by the present disclosure.

Various electronic devices or smart devices may have transducers,speakers, and acoustic output transducers, for example any transducerfor converting a suitable electrical driving signal into an acousticoutput such as a sonic pressure wave or mechanical vibration. Forexample, many electronic devices may include one or more speakers orloudspeakers for sound generation, for example, for playback of audiocontent, voice communications and/or for providing audiblenotifications.

Such speakers or loudspeakers may comprise an electromagnetic actuator,for example a voice coil motor, which is mechanically coupled to aflexible diaphragm, for example a conventional loudspeaker cone, orwhich is mechanically coupled to a surface of a device, for example theglass screen of a mobile device. Some electronic devices may alsoinclude acoustic output transducers capable of generating ultrasonicwaves, for example for use in proximity detection-type applicationsand/or machine-to-machine communication.

Many electronic devices may additionally or alternatively include morespecialized acoustic output transducers, for example, haptictransducers, tailored for generating vibrations for haptic controlfeedback or notifications to a user. Additionally or alternatively, anelectronic device may have a connector, e.g., a socket, for making aremovable mating connection with a corresponding connector of anaccessory apparatus, and may be arranged to provide a driving signal tothe connector so as to drive a transducer, of one or more of the typesmentioned above, of the accessory apparatus when connected. Such anelectronic device will thus comprise driving circuitry for driving thetransducer of the host device or connected accessory with a suitabledriving signal. For acoustic or haptic transducers, the driving signalmay generally be an analog time varying voltage signal, for example, atime varying waveform.

FIG. 3 illustrates selected components of an example host device 300incorporating force sensing using an electromagnetic load 301 of hostdevice 300, in accordance with embodiments of the present disclosure.Host device 300 may include, without limitation, a mobile device, homeapplication, vehicle, and/or any other system, device, or apparatus thatincludes a human-machine interface. Electromagnetic load 301 may includeany suitable load with a complex impedance, including without limitationa haptic transducer, a loudspeaker, a microspeaker, a piezoelectrictransducer, or other suitable transducer.

In operation, a signal generator 324 of a processing subsystem 305 ofhost device 300 may generate a raw transducer driving signal x′ (t)(which, in some embodiments, may be a waveform signal, such as a hapticwaveform signal or audio signal). Raw transducer driving signal x′ (t)may be generated based on a desired playback waveform received by signalgenerator 324.

Raw transducer driving signal x′ (t) may be received by waveformpreprocessor 326 which, as described in greater detail below, mayoptimize raw transducer driving signal x′ (t) based on an estimatedback-electromotive force (EMF) voltage V_(B)(t) in order to generateprocessed transducer driving signal x(t) to account for variations inproduction tolerance, operating conditions, design differences ofelectromagnetic load 301, temperature, and/or other parameters in orderto attempt to create a uniform perception (e.g., force or accelerationevent) across host devices 300 or platforms (e.g., overcoming productionvariations in electromagnetic load 301 and haptics subsystems) and evendifferent device 100 and platform designs.

Processed transducer driving signal x(t) may in turn be amplified byamplifier 306 to generate a driving signal V(t) for drivingelectromagnetic load 301. Responsive to driving signal V(t), a sensedterminal voltage V_(T)(t) of electromagnetic load 301 may be sensed by aterminal voltage sensing block 307, for example a volt-meter, andconverted to a digital representation by a first analog-to-digitalconverter (ADC) 303. Similarly, sensed current I(t) may be converted toa digital representation by a second ADC 304. Current I(t) may be sensedacross a shunt resistor 302 having resistance R_(s) coupled to aterminal of electromagnetic load 301.

As shown in FIG. 3 , processing subsystem 305 may include a back-EMFestimate block 308 that may estimate back-EMF voltage V_(B)(t). Ingeneral, back EMF voltage V_(B)(t) may not be directly measured fromoutside of the haptic transducer. However, the terminal voltage V_(T)(t)measured at the terminals of the haptic transducer may be related toV_(B)(t) by:

$\begin{matrix}{{V_{T}(t)} = {{V_{B}(t)} + {{Re} \cdot {I(t)}} + {{Le} \cdot \frac{{dI}(t)}{dt}}}} & (2)\end{matrix}$where the parameters are defined as described with reference to FIG. 2 .Consequently, back-EMF voltage V_(B)(t) may be estimated according toequation (2) which may be rearranged as:

$\begin{matrix}{{V_{B}(t)} = {{V_{T}(t)} - {{Re} \cdot {I(t)}} - {{Le}\frac{{dI}(t)}{dt}}}} & (3)\end{matrix}$Because back-EMF voltage V_(B)(t) may be proportional to velocity of themoving mass of electromagnetic load 301, back-EMF voltage V_(B)(t) mayin turn provide an estimate of such velocity. Thus, back-EMF voltageV_(B)(t) may be estimated based on an equivalent electrical model ofelectromagnetic load 301, and such electrical model may vary onparameters of electromagnetic load 301 and host device 300 includingresonant frequency and quality factor.

In some embodiments, back-EMF estimate block 308 may be implemented as adigital filter with a proportional and parallel difference path. Theestimates of DC resistance Re and inductance Le may not need to beaccurate (e.g., within an approximate 10% error may be acceptable), andthus, fixed values from an offline calibration or from a data sheetspecification may be sufficient. As an example, in some embodiments,back-EMF estimate block 308 may determine estimated back-EMF voltageV_(B)(t) in accordance with the teachings of U.S. patent applicationSer. No. 16/559,238, filed Sep. 3, 2019, which is incorporated byreference herein in its entirety.

The relationship among estimated back-EMF voltage V_(B)(t), magneticforce factor Bl, and an estimated velocity u(t) of a moving mass ofelectromagnetic load 301 may be determined from the relationship:V _(B)(t)=Bl·u(t)

Further, a force experienced by a user of host device 300 as a result ofa haptic event may be proportional to an acceleration of the moving massof electromagnetic load 301, and because acceleration is a mathematicalderivative with respect to time of velocity, acceleration resulting froma haptic event of electromagnetic load 301 may be approximatelyproportional to the mathematical derivative with respect to time ofestimated back-EMF voltage V_(B).

Accordingly, waveform preprocessor 326 may (e.g., during usage of hostdevice 300, power-up of host device 300, and/or production of hostdevice 300) receive a signal indicative of estimated back-EMF voltageV_(B)(t) and from such signals, determine an approximate acceleration ofthe moving mass of electromagnetic load 301. Once such approximateacceleration is known, waveform preprocessor 326 may be configured tocompare such actual approximate acceleration to raw transducer drivingsignal x′(t), which may be indicative of a desired acceleration profilefor electromagnetic load 301, and generate processed transducer drivingsignal x(t) from raw transducer driving signal x′ (t) based on theactual approximate acceleration to account for variations in productiontolerance, operating conditions, design differences of electromagneticload 301, temperature, and/or other parameters in order to attempt tocreate a uniform perception (e.g., force or acceleration event) acrosshost devices 300 or platforms (e.g., overcoming production variations inelectromagnetic load 301 and haptics subsystems) and even differentdevice 100 and platform designs. To generate processed transducerdriving signal x(t) from raw transducer driving signal x′ (t), waveformpreprocessor 326 may modify raw transducer driving signal x′ (t) in anysuitable manner (e.g., by applying appropriate gains and/or filterresponses).

FIG. 4 illustrates a flow chart of an example method for reproducing ahaptic waveform at electromagnetic load 301, in accordance withembodiments of the present disclosure. According to some embodiments,method 400 may begin at step 402. As noted above, teachings of thepresent disclosure may be implemented in a variety of configurations ofhost device 300. As such, the preferred initialization point for method400 and the order of the steps comprising method 400 may depend on theimplementation chosen.

At step 402, back-EMF estimate block 308 may receive signals indicativeof sensed terminal voltage V_(T)(t) and sensed current I(t) associatedwith electromagnetic load 301. At step 404, based on sensed terminalvoltage V_(T)(t) and sensed current I(t), back-EMF estimate block 308may generate a signal indicative of estimated back-EMF voltage V_(B)(t).At step 406, waveform preprocessor 326 may determine an approximateacceleration of the moving mass of electromagnetic load 301 based onestimated back-EMF voltage V_(B)(t). At step 408, waveform preprocessor326 may process raw transducer driving signal x′(t) based on estimatedback-EMF voltage V_(B)(t) in order to generate processed transducerdriving signal x(t) in order to reproduce a desired acceleration profilefor electromagnetic load 301 as indicated by raw transducer drivingsignal x′(t) despite physical or other variances of electromagnetic load301 and/or host device 300 that may cause such acceleration ofelectromagnetic load 301 to vary from the desired acceleration profile.After completion of step 408, method 400 may proceed again to step 402.

Although FIG. 4 discloses a particular number of steps to be taken withrespect to method 400, method 400 may be executed with greater or fewersteps than those depicted in FIG. 4 . In addition, although FIG. 4discloses a certain order of steps to be taken with respect to method400, the steps comprising method 400 may be completed in any suitableorder.

Method 400 may be implemented in whole or part using host device 300and/or any other system operable to implement method 400. In certainembodiments, method 400 may be implemented partially or fully insoftware and/or firmware embodied in computer-readable media.

In some embodiments, waveform preprocessor 326 may modify raw transducerdriving signal x′(t) to generate processed transducer driving signalx(t) based on instantaneous haptic events and/or previous haptic events(e.g., sensed terminal voltage V_(T)(t), sensed current I(t), estimatedback-EMF voltage V_(B)(t), DC resistance Re, and inductance Le), thusallowing for learning and adaptation of a response of waveformpreprocessor 326.

As used herein, when two or more elements are referred to as “coupled”to one another, such term indicates that such two or more elements arein electronic communication or mechanical communication, as applicable,whether connected indirectly or directly, with or without interveningelements.

This disclosure encompasses all changes, substitutions, variations,alterations, and modifications to the example embodiments herein that aperson having ordinary skill in the art would comprehend. Similarly,where appropriate, the appended claims encompass all changes,substitutions, variations, alterations, and modifications to the exampleembodiments herein that a person having ordinary skill in the art wouldcomprehend. Moreover, reference in the appended claims to an apparatusor system or a component of an apparatus or system being adapted to,arranged to, capable of, configured to, enabled to, operable to, oroperative to perform a particular function encompasses that apparatus,system, or component, whether or not it or that particular function isactivated, turned on, or unlocked, as long as that apparatus, system, orcomponent is so adapted, arranged, capable, configured, enabled,operable, or operative. Accordingly, modifications, additions, oromissions may be made to the systems, apparatuses, and methods describedherein without departing from the scope of the disclosure. For example,the components of the systems and apparatuses may be integrated orseparated. Moreover, the operations of the systems and apparatusesdisclosed herein may be performed by more, fewer, or other componentsand the methods described may include more, fewer, or other steps.Additionally, steps may be performed in any suitable order. As used inthis document, “each” refers to each member of a set or each member of asubset of a set.

Although exemplary embodiments are illustrated in the figures anddescribed below, the principles of the present disclosure may beimplemented using any number of techniques, whether currently known ornot. The present disclosure should in no way be limited to the exemplaryimplementations and techniques illustrated in the drawings and describedabove.

Unless otherwise specifically noted, articles depicted in the drawingsare not necessarily drawn to scale.

All examples and conditional language recited herein are intended forpedagogical objects to aid the reader in understanding the disclosureand the concepts contributed by the inventor to furthering the art, andare construed as being without limitation to such specifically recitedexamples and conditions. Although embodiments of the present disclosurehave been described in detail, it should be understood that variouschanges, substitutions, and alterations could be made hereto withoutdeparting from the spirit and scope of the disclosure.

Although specific advantages have been enumerated above, variousembodiments may include some, none, or all of the enumerated advantages.Additionally, other technical advantages may become readily apparent toone of ordinary skill in the art after review of the foregoing figuresand description.

To aid the Patent Office and any readers of any patent issued on thisapplication in interpreting the claims appended hereto, applicants wishto note that they do not intend any of the appended claims or claimelements to invoke 35 U.S.C. § 112(f) unless the words “means for” or“step for” are explicitly used in the particular claim.

What is claimed is:
 1. A system comprising: an electromagnetic loadcapable of generating a haptic event; and a haptic processor configuredto process at least one first parameter indicative of a desiredperception of the haptic event to a user of a device comprising theelectromagnetic load and at least one second parameter indicative of anequivalent model of the electromagnetic load to generate a drivingsignal to the electromagnetic load in order to produce the desiredperception to the user despite variances in the device that cause anactual perception of the haptic event to vary from the desiredperception.
 2. The system of claim 1, wherein the at least one firstparameter is indicative of a desired acceleration of the device.
 3. Thesystem of claim 2, wherein the system comprises a waveform generatorconfigured to generate a driving waveform based on the desiredacceleration.
 4. The system of claim 3, wherein generating the drivingsignal comprises generating the driving signal by modifying the drivingwaveform based on the at least one second parameter.
 5. The system ofclaim 1, wherein the equivalent model is an equivalent electrical modelof the electromagnetic load.
 6. The system of claim 1, wherein the atleast one second parameter is indicative of at least one among aresonant frequency and quality factor of the electromagnetic load. 7.The system of claim 1, wherein the at least one second parameter isindicative of a back-electromotive force associated with theelectromagnetic load.
 8. The system of claim 1, wherein the at least onesecond parameter is indicative of a current haptic event and ahistorical haptic event associated with the device.
 9. The system ofclaim 1, wherein the at least one second parameter is determined duringat least one among usage of the device by the user, power-up of thedevice, and production of the device.
 10. The system of claim 1, whereinthe electromagnetic load comprises a haptic transducer.
 11. A methodcomprising processing at least one first parameter indicative of adesired perception of a haptic event to a user of a device comprising anelectromagnetic load capable of generating the haptic event and at leastone second parameter indicative of an equivalent model of theelectromagnetic load to generate a driving signal to the electromagneticload in order to produce the desired perception to the user despitevariances in the device that cause an actual perception of the hapticevent to vary from the desired perception.
 12. The method of claim 11,wherein the at least one first parameter is indicative of a desiredacceleration of the device.
 13. The method of claim 12, furthercomprising generating a driving waveform based on the desiredacceleration.
 14. The method of claim 13, wherein generating the drivingsignal comprises generating the driving signal by modifying the drivingwaveform based on the at least one second parameter.
 15. The method ofclaim 11, wherein the equivalent model is an equivalent electrical modelof the electromagnetic load.
 16. The method of claim 11, wherein the atleast one second parameter is indicative of at least one among aresonant frequency and quality factor of the electromagnetic load. 17.The method of claim 11, wherein the at least one second parameter isindicative of a back-electromotive force associated with theelectromagnetic load.
 18. The method of claim 11, wherein the at leastone second parameter is indicative of a current haptic event and ahistorical haptic event associated with the device.
 19. The method ofclaim 11, wherein the at least one second parameter is determined duringat least one among usage of the device by the user, power-up of thedevice, and production of the device.
 20. The method of claim 11,wherein the electromagnetic load comprises a haptic transducer.
 21. Themethod of claim 11, wherein the equivalent model is an equivalentmechanical model of the electromagnetic load.
 22. The system of claim 1,wherein the equivalent model is an equivalent mechanical model of theelectromagnetic load.
 23. The method of claim 11, wherein the equivalentmodel is a linear model of the electromagnetic load.
 24. The system ofclaim 1, wherein the equivalent model is a linear model of theelectromagnetic load.